Since Congreve's books had been incorporated with the Leeds library in 1740, we can understand how eighty-two of the identical editions in the list could turn up in sales of Leeds books in 1930. Most of the eighty-two exact editions named (and many of the thousands of unnamed books) in these sales were probably once Congreve's. The fact that Sotheby's catalogue mentions the Congreve signature in only ten books suggests that he usually failed to write his name in his books. Sotheby lists most of the books for which Congreve is known to have subscribed, and yet no mention is made of a Congreve signature in any of them. Nor does any signature appear in the special edition of Rowe's Shakespeare (Number 544 in the list) now in the Folger Shakespeare Library and almost certainly once Congreve's.
But other books besides the ten mentioned by Sotheby's were signed by Congreve. One example is Sotheby's item Number 532 (Congreve's Number 518), which was sold to McLeish and Sons and then to E. S. de Beer, Esq., before the unmistakable signature of the dramatist was noted. Another example is Congreve's Number 501, which was in the Hornby Castle Sale and bears the true signature, "Wm: Congreve." Especially significant is a letter to the editor dated August 20, 1949, from Her Grace Katherine, Duchess of the tenth Duke of Leeds, stating that many years ago she had herself "made a great hunt for any books at Hornby Castle bearing the signature of Congreve," had found "numbers" of them, and had made a full catalogue with the aid of "Mr. Charles Whibley, the writer & bibliophile." Unfortunately this catalogue has been lost. If it is ever found, it will be an interesting record of autographed Congreve books held together by one family for nearly two centuries. But the catalogue could not include all the items on the Congreve list since, as we have seen, the dramatist evidently owned many books in which he failed to write his name.
In the twenty-odd books known to have been autographed by the dramatist, the signature is commonly "Will: Congreve," but the surname is sometimes preceded by "W," "Wm," "Willm," "Gul," "Gulielmi," or "Gulielmus." One of Congreve's books (Number 236 in the list) preserved in the Yale Library uses both "W: Congreve" and "Gulielmus Congreve" in different signatures. None of the signatures should be accepted as that of the dramatist until the handwriting is verified, for "William" has long been a common Christian name in the Congreve family. In 1700 there were living no fewer than five Congreves bearing this name, all descended from the same grandfather. One of these was Colonel William Congreve (1671-1746) of Highgate, a cousin of the dramatist, whose papers have been confused with those of the dramatist in many sales as well as in many American libraries. The colonel usually signed "Will:" as did the dramatist, but the two cousins formed the "W" in strikingly different ways. The colonel rounded the first upper prong of this letter and brought the middle prong to only little more than half the height of the other prongs; the dramatist sharpened the first prong and brought the middle prong fully up to the height of the others.